Films coated with paint

ABSTRACT

The present invention relates to films which are coated with at least two paint coats ( 2 ) ( 3 ), whereby the backing film ( 1 ) is coated with at least one radiation-hardenable paint coat ( 2 ) and at least one second paint coat ( 3 ), which can harden at least partially without radiation. The invention also relates to a method for producing said films and to their use for coating steel, aluminium and plastic substrates.

[0001] The present invention relates to films coated with at least twopaint layers, to a process for producing the films, and to their use.

[0002] With the nowadays customary wet-chemical finishing by way ofspraying techniques it is extremely difficult to produce matching-colorcoatings on different substrates such as steel, aluminum, and plastic.The motor vehicle industry in particular is therefore interested indeveloping new finishing technologies for this area.

[0003] Films are being discussed as a long-term alternative to theconventional wet finishing. Coating with films can both economically andenvironmentally be an interesting future technology as an alternative towet finishing. Paint from the roll, guaranteeing consistent colorquality, enables a modular, site-independent production regime to beimplemented, with corresponding cost savings in manufacture. With thefilm coating of rail vehicles as well there are savings: for example,the application of multicolor contrast stripes requires for each colorthe operations of masking, spraying, and drying for 1 to 2 days. Thisentails expensive factory standing times. Through the direct laminationof colored paint film stripes it is possible to reduce significantly thestanding times and the labor involved. As well as economic aspects thereare environmental incentives as well: no emission problems with solventin the painting plant, and eco-friendly coating through solventrecycling in the coating operation.

[0004] In the prior art a variety of possible solutions have alreadybeen discussed. For instance, EP-A-374551 discloses coated substratessuitable for producing body-mounted components for automobile bodies.The coated substrates described in EP-A-374551 consist of metal sheetsfinished with at least one paint layer or of composites whose surfacelayer is composed of the painted metal sheets. DE-4424290.9-A1discloses, further, substrates coated with two or more layers. Thesesubstrates are deformed and processed further with the aid, whereappropriate, of additional materials. In this way it is possible toproduce body-mounted components for vehicle bodies.

[0005] Films coated with coating materials are also described in EP0395226, EP 0361823, U.S. Pat. No. 5,268,215, U.S. Pat. No. 6,063,230,DE 19526478 A1, and DE 3042156 A1.

[0006] A very wide variety of materials have been conceived as carrierfilms. From DE-4319519 A1, U.S. Pat. No. 4,933,237, and EP 0285071, forexample, the use of polyester films is known.

[0007] Thermal coating materials are extensively used for the coating ofthe carrier films. However, coating materials curable with UV radiationhave also been trialed. Such materials are described in, for example, DE19535935 A1 and DE 4439350 A1.

[0008] Different adhesion promoters have been described for theapplication of the carrier films: reference may be made in this context,for example, to DE 4319519 A1 and U.S. Pat. No. 4,933,237.

[0009] The coated films known to date have a variety of drawbacks. Theseconcern in particular the thermoformability and the consistency ofshade. Problems are also presented by the joining of the individualpaint layers and the adhesion to the substrate. Finally, in terms ofmechanical stability, the film paints have not to date been able tomatch conventional spray paints.

[0010] That is, the requirements in terms of fracture resistance,scratch resistance, chemical resistance, and weathering stability havenot to date been met by the coated films. It has likewise not beenpossible so far to produce metallic effects in spray paint quality.

[0011] It is an object of the present invention, accordingly, to providefilms coated with at least two paint layers, constituting a usefulalternative to the hitherto customary liquid paints. The coldformability and thermoformability of the films and the consistency ofshade, in particular, ought to be ensured. Additionally, improvedadhesion of the individual paint layers ought to be achieved. Finally,in terms of the mechanical strength, and in particular with regard tothe fracture resistance, an improvement ought to be obtained over theprior art. At the same time the paint layers ought to exhibit scratchresistance, chemical resistance, and weathering stability comparablewith those of the existing liquid paints. An objective of the invention,moreover, is to produce metallic effects in a quality which matches thatof the existing spray paint. Finally, it is an object of the inventionto produce films which can be removed again without residues.

[0012] The inventive solution are films coated with at least two paintlayers, wherein a carrier film bears at least one first paint layer,which is radiation-curable, and at least one second paint layer, whichis curable at least partly without radiation exposure. The second paintlayer is therefore preferably at least partly thermally curable.

[0013] The radiation-curable paints are used particularly for the firstpaint layer. Preference is given to using radiation-curable clearcoatpaints. It is also possible, however, to color and/or to pigment theclearcoat paints.

[0014] Clearcoat paints used are compositions curable with high-energyradiation, such as UV radiation or electron beams, especially UVradiation. A key constituent of such clearcoat paints is at least oneradiation-curable oligomeric or polymeric binder.

[0015] The oligomers or polymers used as binders usually have anumber-average molecular weight of from 500 to 50 000, preferably from 1000 to 5 000. They preferably have a double bond equivalent weight offrom 300 to 2 000, more preferably from 400 to 900. Furthermore, thefully formulated binders have a viscosity at 23° C. of preferably from250 to 11 000 mPas. They are preferably employed in an amount of from 5to 50% by weight, more preferably from 6 to 45% by weight, morepreferably still from 7 to 40% by weight, very preferably from 8 to 35%by weight, and in particular from 9 to 30% by weight, based in each caseon the solids of the clearcoat paint.

[0016] Examples of suitable binders come from the oligomer and/orpolymer classes of (meth)acryloyl-functional (meth)acrylic copolymers,polyether acrylates, polyester acrylates, polyesters, epoxy acrylates,urethane acrylates, amino acrylates, melamine acrylates, siliconeacrylates, and phosphazene acrylates, and the correspondingmethacrylates, as described in, for example, German patent DE 197 09 467C1, page 4 line 36 to page 5 line 61. It is preferred to use bindersfree from aromatic structural units. Preference is therefore given tousing urethane (meth)acrylates, phosphazene (meth)acrylates and/orpolyester (meth)acrylates, more preferably urethane (meth)acrylates,especially aliphatic urethane (meth)acrylates.

[0017] The urethane (meth)acrylates are obtained by reacting adiisocyanate or polyisocyanate with a chain extender from the groupconsisting of diols/polyols and/or diamines/polyamines and/ordithiols/polythiols and/or alkanolamines and subsequently reacting theremaining free isocyanate groups with at least one hydroxyalkyl(meth)acrylate or hydroxyalkyl ester of other ethylenically unsaturatedcarboxylic acids.

[0018] The amounts of chain extenders, di- and/or polyisocyanates, andhydroxyalkyl esters are preferably chosen such that

[0019] 1.) the equivalent ratio of the NCO groups to the reactive groupsof the chain extender (hydroxyl, amino and/or mercaptyl groups) isbetween 4:1 and 1:2, preferably between 3:1 and 3:2, and

[0020] 2.) the OH groups of the hydroxyalkyl esters of the ethylenicallyunsaturated carboxylic acids are present in a stoichiometric amount withrespect to the remaining free isocyanate groups of the prepolymer formedfrom isocyanate and chain extender.

[0021] A further option is to prepare the urethane (meth)acrylates byfirst reacting some of the isocyanate groups of the diisocyanate orpolyisocyanate with at least one hydroxyalkyl ester and subsequentlyreacting the remaining isocyanate groups with a chain extender. In thiscase too the amounts of chain extender, isocyanate, and hydroxyalkylester are chosen such that the equivalent ratio of the NCO groups to thereactive groups of the chain extender is between 4:1 and 1:2, preferablybetween 3:1 and 3:2, and the equivalent ratio of the remaining NCOgroups to the OH groups of the hydroxyalkyl ester is 1:1. It will beappreciated that any forms intermediate between these two methods arealso possible. For example, some of the isocyanate groups of adiisocyanate can first be reacted with a diol, then a further fractionof the isocyanate groups can be reacted with the hydroxyalkyl ester,after which the remaining isocyanate groups can be reacted with adiamine.

[0022] Flexibilization of the urethane (meth)acrylates is possible, forexample, by reacting corresponding isocyanate-functional prepolymers oroligomers with relatively long-chain aliphatic diols and/or diamines,especially aliphatic diols and/or diamines having at least 6 carbonatoms. This flexibilization reaction can be conducted before or afterthe addition reaction of acrylic and/or methacrylic acid with theoligomers and/or prepolymers.

[0023] As examples of suitable urethane (meth)acrylates mention may bemade, among others, of the following, commercially available,polyfunctional aliphatic urethane acrylates:

[0024] Crodamer® UVU 300 from Croda Resins Ltd., Kent, United Kingdom;

[0025] Genomer® 4302, 4235, 4297 or 4316 from Rahn Chemie, Switzerland;

[0026] Ebecryl® 284, 294, IRR 351, 5129 or 1290 from UCB, Drogenbos,Belgium;

[0027] Roskydal® LS 2989 or LS 2545 or V94-504 from Bayer AG, Germany;

[0028] Viaktin® VTE 6160 from Vianova, Austria; or

[0029] Laromer® 8861 from BASF AG and experimental modificationsthereof.

[0030] The systems listed here are liquid as 100% formulations. Theconverse of this is the urethane acrylate system we use with preferencewhich is solid in the 100% state, advantageous for storage andtransport. Castable solutions are produced on site from the solid resin.Solvents suitable for this purpose include THF, acetone, MEK, and MIBK.

[0031] Hydroxyl-containing urethane (meth)acrylates are known from, forexample, patent U.S. Pat. No. 4,634,602 A or U.S. Pat. No. 4,424,252 A.

[0032] One example of a suitable polyphosphazene (meth)acrylate is thephosphazene dimethacrylate from Idemitsu, Japan.

[0033] In addition, the clearcoat paints can comprise the additives,photoinitiators, and reactive diluents described in German patent DE 19709 467 C1, page 5 line 62 to page 6 line 30, including additives such aslight stabilizers, slip additives, polymerization inhibitors, flattingagents, defoamers, leveling agents, and film-forming auxiliaries.

[0034] In order to prevent the formation of bubbles due to excessivelyrapid solvent release during the drying operation it is possible withpreference to add high boilers to the clearcoat paint. Their fractioncan amount to from 5% to 60%, preferably from 10% to 30%. High boilerswhich can be used include dioxane, toluene, and ethyl acetate; butylacetate is employed with preference.

[0035] The layer thickness of the clearcoat paints is from 1 μm to 400am, preferable 5 μm to 100 μm, more preferably 15 μm to 60 μm. Inprinciple the choice of layer thickness depends on the stretching of thefilm. The minimum layer thicknesses stated refer to the end product,i.e., a generally stretched film.

[0036] The paints which can be cured at least partly without radiationpreferably comprise the color layers, which at the same time form thetopcoat layer. Here it is also possible to employ the automotiverefinish paints known from the prior art, on the basis of their goodphysical drying properties and ready availability.

[0037] Suitable refinish paints are one-component or multicomponentsystems. Two-component systems comprise, as is known, at least onecompound, in particular a binder, having isocyanate-reactive functionalgroups, such as thiol, hydroxyl, and primary and secondary amino groups,especially hydroxyl groups, and at least one polyisocyanate.

[0038] Examples of suitable binders are random, alternating and/orblock, linear and/or branched and/or comb addition (co)polymers ofethylenically unsaturated monomers, or polyaddition resins and/orpoly-condensation resins. For further details of these terms refer toRömpp Lexikon Lacke und Druckfarben, Georg Thieme Verlag, Stuttgart,N.Y., 1998, page 457, “polyaddition” and “polyaddition resins(polyadducts)”, and also pages 463 and 464, “polycondensates”,“polycondensation”, and “polycondensation resins”, and also pages 73 and74, “binders”.

[0039] Examples of suitable addition (co)polymers are (meth)acrylate(co)polymers or partially hydrolyzed polyvinyl esters, especially(meth)acrylate copolymers.

[0040] Examples of suitable polyaddition resins and/or polycondensationresins are polyesters, alkyds, polyurethanes, polylactones,polycarbonates, polyethers, epoxy resin-amine adducts, polyureas,polyamides, polyimides, polyester-polyurethanes, polyether-polyurethanesor polyester-polyether-polyurethanes, especiallypolyester-polyurethanes.

[0041] Of these binders, the (meth)acrylate (co)polymers have particularadvantages and are therefore used with particular preference.

[0042] Preparation processes for (meth)acrylate copolymers are describedin European patent application EP 0 767 185 A1, German patent DE 22 14650 B1 or DE 27 49 576 B1, and American patents U.S. Pat. No. 4,091,048A1, U.S. Pat. No. 3,781,379 A1, U.S. Pat. No. 5,480,493 A1, U.S. Pat.No. 5,475,073 A1 or U.S. Pat. No. 5,534,598 A1 or in the standard workHouben-Weyl, Methoden der organischen Chemie, 4th edition, volume 14/1,pages 24 to 255, 1961. Suitable reactors for the copolymerizationinclude the conventional stirred tanks, stirred tank cascades, tubereactors, loop reactors or Taylor reactors, as described in, forexample, the patents and patent applications DE 1 071 241 B1, EP 0 498583 A1 or DE 198 28 742 A1 or in the article by K. Kataoka in ChemicalEngineering Science, volume 50, issue 9, 1995, pages 1409 to 1416.

[0043] The fraction of binders in the refinish paints may vary widelyand is guided by the requirements of the case in hand. They arepreferably employed in an amount of from 5 to 90% by weight, morepreferably from 6 to 80% by weight, more preferably still from 7 to 70%by weight, very preferably from 8 to 60% by weight, and in particularfrom 9 to 50% by weight, based in each case on the solids of therefinish paint.

[0044] The polyisocyanates may have aliphatic, cycloaliphatic oraromatic parent structures. It is also possible, however, for at leasttwo of these structures to be present in one polyisocyanate. Forexample, a polyisocyanate is considered aliphatic if its isocyanategroups are directly connected exclusively to aliphatic groups. Where theisocyanate groups are directly connected both to aliphatic and tocycloaliphatic groups, the polyisocyanate in question is analiphatic-cycloaliphatic polyisocyanate.

[0045] Preference is given to using aliphatic, aliphatic-cycloaliphatic,cycloaliphatic, and aromatic polyisocyanates.

[0046] The aromatic polyisocyanates are preferably used when a certainyellowing tendency can be tolerated in the films of the invention. Wherethe absence of yellowing is very critical, on the other hand, it ispreferred to use aliphatic, cycloaliphatic, andaliphatic-cyclo-aliphatic polyisocyanates.

[0047] Examples of suitable polyisocyanates are isocyanato-containingpolyurethane prepolymers, which can be prepared by reacting polyols withan excess of aliphatic, aliphatic-cycloaliphatic, cycloaliphatic, andaromatic diisocyanates and are preferably of low viscosity.

[0048] Examples of suitable aromatic diisocyanates include tolylidene2,4- or 2,6-diisocyanate, phenylene 1,2-, 1,3- or 1,4-diisocyanate,naphthylene 1,2-, 1,3- or 1,4-diisocyanate ordi(4-isocyanatophen-1-yl)methane or -propane.

[0049] Examples of suitable aliphatic, cycloaliphatic, andaliphatic-cycloaliphatic diisocyanates are isophorone diisocyanate(i.e., 5-isocyanato-1-isocyanatomethyl-1,3,3-trimethylcyclohexane),5-isocyanato-1-(2-iso-cyanatoeth-1-yl)-1,3,3-trimethylcyclohexane,5-iso-cyanato-1-(3-isocyanatoprop-1-yl)-1,3,3-trimethylcyclo-hexane,5-isocyanato-(4-isocyanatobut-1-yl)-1,3,3-trimethylcyclohexane,1-isocyanato-2-(3-isocyanatoprop-1-yl)cyclohexane,1-isocyanato-2-(3-isocyanatoeth-1-yl)cyclohexane,1-isocyanato-2-(4-isocyanatobut-1-yl)-cyclohexane,1,2-diisocyanatocyclobutane, 1,3-diisocyanatocyclobutane,1,2-diisocyanatocyclopentane, 1,3-diisocyanatocyclopentane,1,2-diisocyanatocyclohexane, 1,3-diisocyanatocyclohexane,1,4-diisocyanatocyclohexane, dicyclohexylmethane 2,4′-diisocyanate,tri-methylene diisocyanate, tetramethylene diisocyanate, pentamethylenediisocyanate, hexamethylene diioscyanate (HDI), ethylethylenediisocyanate, trimethylhexane diisocyanate, heptamethylene diisocyanate,methylpentane diisocyanate (MPDI), nonane triisocyanate (NTI) ordiisocyanates derived from dimer fatty acids, as sold under thecommercial designation DDI 1410 by Henkel and described in patents WO97/49745 and WO 97/49747, especially2-heptyl-3,4-bis(9-isocyanatononyl)-1-pentylcyclohexane, or 1,2-, 1,4-or 1,3-bis(isocyanatomethyl)cyclohexane, 1,2-, 1,4- or1,3-bis(2-isocyanatoeth-1-yl)cyclohexane,1,3-bis(3-iso-cyanatoprop-1-yl)cyclohexane, 1,2-, 1,4- or1,3-bis(4-isocyanatobut-1-yl)cyclohexane or liquidbis(4-iso-cyanatocyclohexyl)methane with a trans/trans content of up to30% by weight, preferably 25% by weight, and in particular 20% byweight, as described by patent applications DE 44 14 032 A1, GB 1220717A1, DE 16 18 795 A1 or DE 17 93 785 A1, preferably isophoronediisocyanate,5-isocyanato-1-(2-isocyanato-eth-1-yl)-1,3,3-trimethylcyclohexane,5-isocyanato-1-(3-isocyanatoprop-1-yl)-1,3,3-trimethylcyclohexane,5-isocyanato-(4-isocyanatobut-1-yl)-1,3,3-trimethylcyclohexane,1-isocyanato-2-(3-isocyanatoprop-1-yl)cyclohexane,1-isocyanato-2-(3-isocyanatoeth-1-yl)cyclohexane,1-isocyanato-2-(4-isocyanatobut-1-yl)cyclohexane or HDI, especially HDI.

[0050] It is also possible to use polyisocyanates (B) containingisocyanurate, biuret, allophanate, imino-oxadiazinedione, urethane,urea, carbodiimide and/or uretdione groups, prepared in conventionalmanner from the above-described diisocyanates. Examples of suitablepreparation processes and polyisocyanates are known from, for example,patents CA 1,163,591 A, U.S. Pat. No. 4,419,513, U.S. Pat. No. 4,454,317A, EP 0 646 608 A, U.S. Pat. No. 4,801,675 A, EP 0 183 976 A1, DE 40 15155 A1, EP 0 303 150 A1, EP 0 496 208 A1, EP 0 524 500 A1, EP 0 566 037A1, U.S. Pat. No. 5,258,482 A1, U.S. Pat. No. 5,290,902 A1, EP 0 649 806A1, DE 42 29 183 A1 or EP 0 531 820 A1 or are described in German patentapplication DE 100 05 228.2, unpublished at the priority date of thepresent specification.

[0051] Further suitable polyisocyanates include the adducts, describedin German patent application DE 196 09 617 A1, of polyisocyanates withoxazolidines, dioxolanes, and dioxanes containing isocyanate-reactivefunctional groups, which still contain free isocyanate groups or areused in combination with other polyisocyanates.

[0052] The amount of polyisocyanates in the coating materials may varyvery widely and is guided by the requirements of the case in hand, inparticular by the amount of isocyanato-reactive groups in theconstituents. The amount is preferably from 5 to 50% by weight, morepreferably 6 to 45% by weight, more preferably still from 7 to 40% byweight, very preferably from 8 to 35% by weight, and in particular from9 to 30% by weight, based in each case on the solids of the coatingmaterial of the invention.

[0053] The refinish paints further comprise constituents which renderthem radiation-curable.

[0054] Examples of suitable radiation-curable constituents are theabove-described radiation-curable binders as used in the clearcoatpaints. The radiation-curable binders may additionally contain theisocyanate-reactive functional groups described above.

[0055] Further examples of suitable radiation-curable constituents areisocyanato acrylates, which contain free isocyanate groups and groupscontaining double bonds.

[0056] Highly suitable double bonds are present in, for example,(meth)acrylate, ethacrylate, crotonate, cinnamate, vinyl ether, vinylester, ethenylarylene, dicyclopentadienyl, norbornenyl, isoprenyl,isopropenyl, allyl or butenyl groups; ethenylarylene ether,dicyclopentadienyl ether, norbornenyl ether, isoprenyl ether,isopropenyl ether, allyl ether or butenyl ether groups; orethenylarylene ester, dicyclopentadienyl ester, norbornenyl ester,isoprenyl ester, isopropenyl ester, allyl ester or butenyl ester groups.Of these, (meth)acrylate groups, especially acrylate groups, are ofparticular advantage and are therefore used with very particularpreference.

[0057] The isocyanato acrylates can be prepared by reacting theabove-described polyisocyanates with compounds which have anisocyanate-reactive functional group and at least one group containingdouble bonds. Examples of suitable compounds of this kind are2-hydroxyethyl acrylate, 2- and 3-hydroxypropyl acrylate, 2-, 3-, and4-hydroxybutyl acrylate, reaction products thereof withepsilon-caprolactone, or allyl alcohol. For further details refer toEuropean patent application EP 0 928 800 A1.

[0058] The refinish paints may further comprise at least one of theadditives described in German patent application DE 199 20 799, page 7line 6 to page 8 line 37.

[0059] Leveling agents are preferably added to the automotive refinishpaints and to the clearcoat paints in order to achieve effectiveclearcoat/colorcoat wetting.

[0060] Examples of suitable leveling agents are described in RömppLexikon Lacke und Druckfarben, Georg Thieme Verlag, Stuttgart, N.Y.,1998, “leveling agents (assistants)”, page 602, or in Johan Bieleman,“Lackadditive” [Additives for coatings], Wiley-VCH, Weinheim, N.Y.,1998, “6.1.2 commercial leveling additives” pages 177 to 181.Flurosurfactants are used with preference. Fluorosurfactants arecommercial products and are sold, for example, by 3M under the brandname Fluorad® FC-171, -129, -170C, -430 or -431.

[0061] The pigmented paints which can be used with preference inaccordance with the invention include those curable thermally and bymeans of radiation (dual cure systems, as they are known). In this case,first, an application of the liquid paints is made. At this stage theyhave a low viscosity. Thermal curing here produces an elastomericcoating which by subsequent crosslinking and radiation exposure can becrosslinked further.

[0062] In this way, for example, from the above-described isocyanateacrylates and the hydroxyl-containing binders it is possible first toproduce a polyurethane network which is subsequently crosslinked, byexposure to radiation, to form polyurethane-polyacrylate.

[0063] The layer thicknesses after the stretching of the topcoat paintsused in accordance with the invention are from 10 μm to 60 μm,preferably from 15 μm to 40 μm. As with the layer thickness of theclearcoat paints, the topcoat layer thickness depends on the chosenstretching.

[0064] For the radiation curing of the clearcoat layer and of thepigmented layer preferential consideration is given to electron beamsand UV radiation. Curing with UV radiation is preferred according to theinvention.

[0065] Where the dual cure systems are employed a particular advantageis the combination of the properties of a conventional 2-componentsystem with a UV-crosslinking system. The elastomeric characteristics atroom temperature achieve very good formability, while after radiationexposure effective crosslinking at the join with the clearcoat paint isobtained. Moreover, in the inventive combination of radiation-curablelayer and at least partly radiation-curable layer, the layers describedexhibit particular adhesion to one another, especially if thelast-mentioned layer is a dual cure system. Nor is this adhesion lostunder thermal or mechanical influences.

[0066] In the development of the subject matter of the invention thelocating of suitable carrier films presented problems. Surprisingly itwas found that especially good results are achieved with unorientedpolypropylene films. These films are readily coatable on coatingmachines and, after the paint system has cured, can be detached from thecarrier film. The formability is excellent. In accordance with theinvention it has now surprisingly been found that, preferably at acarrier film thickness of 75 μm or less, both effective formability andadequate thermal stability are achieved. The invention accordingly usescarrier films which are preferably <100 μm, having more preferably athickness >40 μm. Thicknesses of 50 μm to 70 μm are particularlypreferred. Very particular preference attaches to 50 μm to 60 μm.

[0067] Problems with the thermal stability of the film to be coated canbe reduced by using slip films. It is preferred here to use polyesterfilms in a thickness of from 10 μm to 100 μm. From 18 μm to 75 μm areparticularly preferred.

[0068] The carrier film coated with the paints can be used for coating avery wide variety of substrates. In accordance with the invention it ispreferred here to apply the color layer to the substrate. Following fullcure through exposure to actinic radiation, the outer, carrier film canbe removed.

[0069] The bond to the substrate can be produced using adhesionpromoters. In accordance with the invention it is preferred to useadhesives. In this context it is preferred in turn to use UV-curingadhesives. UV radiation is used here preferably for adjusting theadhesive properties. Adhesives of this kind are commercial products andare sold, for example, by BASF Aktiengesellschaft under the brand nameAcronal® 258 UV. In this case the adhesive layer is preferably appliedto a separate film and after UV coating to the topcoat layer. Thismethod is especially advantageous if the topcoat layer is a dual curesystem.

[0070] Where transparent substrates are used for actinic radiation, fullcrosslinking of the adhesives by means of radiation is possible. Theadhesive properties are in this case adjustable preferably bypreliminary crosslinking by means of actinic radiation. Adhesivessuitable for this purpose are described, for example, in Römpp ChemieLexikon, 9th edition, volume 3, Georg Thieme Verlag, Stuttgart, 1990,“Adhesives”, pages 2252 to 2255. Of these adhesives, theradiation-curable adhesives based on (meth)acrylates or UP resins (cf.Römpp Lexikon Lacke und Druckfarben, Georg Thieme Verlag, Stuttgart,N.Y., 1998, “Unsaturated polyester resins”, pages 591 and 592, or D.Stoye and W. Freitag (Editors), Paint, Coatings and Solvents, Wiley-VCH,Weinheim, N.Y., 2nd, completely revised edition, 1998, “2.8. UnsaturatedPolyester Coatings, 2.8.1. Unsaturated Polyester Binders”, pages 57 to58) and styrene and/or (meth)acrylates are of advantage and aretherefore used with preference. It is also possible for theradiation-curable adhesives to include the radiation-curableconstituents described above.

[0071] UV systems require reinforcing sheets coated on both sides.Conventional pressure-sensitive adhesives can be applied directly to thetopcoat layer.

[0072] The thickness of the adhesives is preferably between 4 μm and 20μm.

[0073] The reinforcing sheet is preferably applied to the adhesivepresent on the pigmented paint layer. Given appropriate reactivity ofthe reinforcing sheet, by adhesion promoters, for example, the adhesivelayer can be omitted. The outer face of the reinforcing sheet ispreferably provided in turn with an adhesive. Up until processing, thisadhesive can be lined with a removable release film.

[0074] With the existing adhesives, the removal of the paint filmscauses problems. Depending on manufacturer, there is a requirement thatthe coated films be removable again from the substrate without residueeven after four years.

[0075] Complete reremovability can be achieved in accordance with theinvention, surprisingly, by virtue of the additional reinforcing sheet.In accordance with the invention this sheet has a thickness ofpreferably between 20 μm and 50 μm. From 20 μm to 30 μm are particularlypreferred. A preferred material is polypropylene.

[0076] An adhesive may be applied to the second paint layer. It can bepoured on, laminated or transferred. Atop it it is possible for there tobe applied a further film having a preferred thickness of ≦1000 μm,preferably ≦500 μm.

[0077] The paint film is cold-formable (deep-drawable) and can thereforebe drawn onto any structured area at room temperature or, whereappropriate, with slight heating in order to facilitate operation. Thefilms coated in accordance with the invention achieve thermoformabilityif a further film is laminated onto the adhesive layer present on thepigmented paint layer. Such further films are generally relatively thickfilms. The invention prefers films from 300 μm to 1 000 μm. From 400 μmto 700 μm are particularly preferred. Particularly suitable for thispurpose are ASA, ABS, and ASA-PC.

[0078] Stable 3D structures can be produced from the assembly bythermoforming. A prerequisite for this is effective drying of thelaminate. The surface properties of gloss, metallic, and flop effectsare unaffected by forming.

[0079] The present invention also relates to a process for producing theabovementioned coated films. In this process the individual paint layerscan be applied either in succession or, preferably, by means ofapproximate simultaneous coating. In the latter process the layers areapplied directly wet on wet at short intervals of time. Thereafter thesystem is dried thermally in a drying tunnel. The purpose of drying is,in particular, to remove the solvent.

[0080] The coated films produced in accordance with the invention can beemployed wherever substrates require painting. Substrates of steel,aluminum, and plastic, in particular, can be coated. One preferredsphere of application is the motor vehicle industry. For rail vehiclesas well, however, i.e., locomotives and cars, the system of theinvention can be used to good effect. The scope of use embraces contraststripes through to full coating systems. A particular advantage here isthe possibility of removing the paint films again. Indeed, in that way,it is possible to produce new partial coatings of the vehicles withparticular ease. The removability is a further advantage in cases ofvandalism, e.g., as a result of daubing or spraying with paint(graffiti). Furthermore, the carrier film can ensure protection of thepaint surfaces until the end product has been produced. Thus, forexample, ready-made bodywork parts can first of all be injectionbackmolded or foam-backed, with the carrier film being removed onlyafter this operation is concluded.

[0081] In the text below the invention is described in more detail withreference to the figures.

[0082]FIG. 1 shows a layer construction made up of carrier film,clearcoat paint, and color paint, and also an adhesive.

[0083]FIG. 2 shows a structure of an inventively coated film withreinforcing sheet.

[0084]FIG. 3 shows a structure of an inventively coated film havingparticularly good thermoforming properties.

[0085]FIG. 4 depicts an application method for producing the inventivelycoated films.

[0086] The coated film 1 depicted in FIG. 1 is composed of apolypropylene carrier film 50 μm thick, a clearcoat 2 40 μm thick, and acolor coat 3 30 μm thick, and also an adhesive 4 20 μm thick. Tests haveindicated that the formability of these coated films is excellent. Atthe same time the thermal stability is sufficient for production. With adrier gradient of 30° C./60° C./105° C., the running and windingbehavior in the coating machine is good.

[0087] The structure reproduced in FIG. 2 shows a polypropylene carrierfilm 1 50 μm thick, and also a UV clearcoat layer 2 40 μm thick, a colorcoat 3 30 μm thick, and an adhesive 4 20 μm thick. Laminated to thisadhesive 4 is a reinforcing sheet 5 of from 25 μm to 50 μm. A furtheradhesive 6 20 μm thick is then used to laminate a removable release film7.

[0088] UV Acronal adhesive (Acronal 248 UV, BASF) was used as adhesive 4and 6. Tests have shown that the coated films adhere effectively attemperatures between −30° C. and +90° C. to substrates such as steel,aluminum, plastic, and primed metal panels. The coated films wereremovable, without tears forming in the coating system on removal.Residues on the substrate were no longer present.

[0089] The structure depicted in FIG. 3 shows a polypropylene film 1 50μm thick, a UV clearcoat 2 40 μm thick, a color layer 3 30 μm thick, anadhesive 4, and a film 8 500 μm thick. In accordance with the invention,Luran S was used for this.

[0090] This coated film was used to conduct thermoforming tests. Aftervery good drying of the assembly, the system was readily formable withretention of the surface quality. Gloss, metallic, and color flopeffects were unaffected by the forming. Formed parts can be injectionbackmolded or foam-backed, in accordance with the invention. In thiscase the protective film is preferably not removed until after formingand radiation crosslinking. The advantage of the present invention istherefore that the surface is protected from scratching during transportand processing by the protective film. The protective film has thefurther advantage that there is no oxygen inhibition on UV crosslinking.

[0091]FIG. 4 depicts by way of example the production of the inventivelycoated films. The carrier film 1, supplied on a roll, is guided beneatha predosed casting system 9. In the example according to FIG. 4 thissystem 9 includes the stations 11 and 12. By way of station 11 theclearcoat 2 is supplied via station 12 to the colorcoat 3. First of allthe clearcoat 2 goes onto the film 1 and by way of station 12 thecolorcoat 3 is applied simultaneously, so to speak, wet-on-wet. Film andpaint layers are then passed through a drier 13. The formation ofbubbles observed from a wet layer application of 30 μm up, as a resultof excessively rapid solvent release in the drier, was eliminated byadapting the temperature in the drying tunnel and by adding 10% of butylacetate (high boiler) to the acetone solution of clearcoat.

[0092] As an alternative the casting system may also be composed of twocasting heads in series but spatially separate. The first caster appliesthe clearcoat layer to the film. Directly, in wet-on-wet process, thetopcoat layer is applied beneath the second casting head. The clearcoatlayer is applied using KRRC processes or, preferably, predosed castersor what are called blade coaters. The topcoat layer is applied usingpredosed casters or, preferably, extrusion casters, with a spreader lipto smooth the coating.

[0093] Irrespective of whether a casting system according to item 9 inFIG. 4 or a system with separate casting units is used, it is necessaryto ensure that no mixing takes place between the boundary layers. Tothis extent the two casting methods described guarantee, in the case ofwet-on-wet application, the absence of mixing of the clearcoat layer andof the topcoat layer.

[0094] After the drier, the coated film is supplied for furtherprocessing.

1. A film coated with at least two paint layers, wherein a carrier filmbears at least one first paint layer, which is radiation-curable, and atleast one second paint layer, which is curable at least partly withoutradiation, and wherein an adhesive layer has been cast, laminated ortransferred onto the second paint layer.
 2. The film as claimed in claim1, wherein the second paint layer is curable thermally and by radiation.3. The film as claimed in claim 1, wherein the first layer is anunpigmented clearcoat layer.
 4. The film as claimed in claim 1, whereinthe second paint layer is a pigmented topcoat layer.
 5. The film asclaimed in claim 1, wherein the first and the second paint layers arecurable by UV radiation.
 6. The film as claimed in claim 1, wherein thefirst paint layer has a thickness of 1 μm-400 μm and the second paintlayer has a thickness of from 10 μm to 60 μm.
 7. The film as claimed inclaim 1, wherein the adhesive properties are adjustable by preliminarycrosslinking with actinic radiation.
 8. The film as claimed in claim 7,wherein the adhesive is curable by UV radiation.
 9. The film as claimedin claim 6, wherein the thickness of the adhesive is 4 μm-20 μm.
 10. Thefilm as claimed in claim 1, wherein the carrier film is formable andthermally stable.
 11. The film as claimed in claim 10, wherein thecarrier film is comprises polypropylene.
 12. The film as claimed inclaim 10, wherein the carrier film has a thickness of from 40 μm to 100μm.
 13. The film as claimed in claim 10, wherein the carrier film has athickness of from 50 μm to 70 μm.
 14. The film as claimed in claim 1,wherein one or more further films have been applied to the adhesivelayer.
 15. The film as claimed in claim 14, wherein one of the furtherfilms is a reinforcing sheet having a thickness of from 25 μm to 50 μm.16. The film as claimed in claim 14, wherein to produce a thermoformableassembly a further film with a thickness of ≦1000 μm is applied to theadhesive layer.
 17. A process for producing the film as claimed in claim1, wherein the first and the second paint layers are applied to thecarrier film by approximate simultaneous coating in a wet-on-wetapplication process and subsequently the solvent is removed from thissystem by thermal drying.
 18. The process as claimed in claim 17,wherein an adhesive-coated release film is laminated or transferred ontothe second paint layer. 19 (Canceled).
 20. A substrate coated with thefilm as claimed in claim 1, wherein the substrate is at least one ofsteel, aluminum or plastic.
 21. A process for coating a substratecomprising, coating a steel, aluminum or plastic substrate with the filmas claimed in claim 1.